Selection, Adaptation, and Evolutionary Genomics

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Research

I am an evolutionary ecologist working in Dr. Daniel Matute‘s lab at UNC, Chapel Hill, interested in understanding how natural selection acts on phenotypic and genetic variation to generate observed patterns of diversity. I am broadly interested in using a wide range of approaches to address a diversity of questions in evolutionary biology. Below are a few current / ongoing projects I am working on.

Evolutionary and behavioural ecology and genetics in Drosophila fruit flies.

Hybridization between diverged or differentiated lineages can have a wide range of effects on their evolution. On the one hand hybridization can introduce maladaptive genetic variation and come at a cost to the hybridizing species or populations, and on the other hand, hybridization can be a generative process, introducing adaptive genetic variation and generating novel genotypic combinations that might actually facilitate adaptation. We are currently using a combination of computer simulations and experimental evolution in Drosophila to test the generality of conditions that are most likely to lead to hybrid speciation. For example, how often does hybridization lead to novel trait combinations that generate reproductive isolation between hybrid linages and their parental species? How do levels of genetic divergence between the parental species influence the likelihood of homoploid hybrid speciation? And what is the genetic basis of reproductive isolation within hybrid lineages? The results of these experiments will help us to better understand the scenarios under which hybridization is expected to be a generative process in evolution.

Specialist or generalist strategies have evolved across the tree of life and many groups of insects that rely on plants for food or breeding sites have evolved to specialize on a small fraction of the total plant species available to them. Given that insects are the most diverse group of animals on Earth, understanding the evolutionary processes underlying their diversification is central to our understanding of biodiversity. We are currently testing the genetic basis of host specialization within the little known species of Drosophila – D. orena – living on the island of Bioko, West Africa. In general, this project combines natural collections, behavioural assays, comparative genomics, and genetics to describe the natural history and genetic basis of specialization in D. orena. The ultimate goal of this work is to build on previous studies of host specialization in other species of insects and provide novel insights into the genetic toolkit used across multiple instances of specialization.

Reinforcement has a long history of study in evolutionary biology and examples of reinforcement’s role in strengthening reproductive isolation between species, potentially ‘completing’ speciation, now exist. Recent studies have also shown that reinforcing selection can drive incidental behavioural divergence between populations of the same species, generating reproductive isolation between them. We are studying the incidental or “cascade” effects of reinforcing selection in the African fruit fly Drosophila yakuba­. Populations of D. yakuba that are found in sympatry with their sister species, D. santomea, show elevated levels of reproductive isolation with D. santomea relative to allopatric populations. We have used a combination of phenotypic assays and experimental evolution to show that reinforcing selection acting within sympatric populations of D. yakuba results in elevated levels of reproductive isolation between conspecific populations found in allopatry. We are also using a combination of genetic and genomic techniques to better understand the genetic basis of reinforcement.

Projects Currently on the Back Burner:

The genetics of adaptive phenotypic variation in Timema stick insects

During my PhD. I worked in Dr. Patrik Nosil’s lab at the University of Sheffield studying the how the genetic architecture of adaptive traits can influence the evolutionary response to natural selection. We specifically focused on color and pattern traits in stick insects of the genus Timema that confer crypsis in different plant environments. Timema are well suited to studies exploring the genomics of adaptation and speciation as species of Timema display a wide range of phenotypic variation and can be found exploiting a diverse array of host plant species. We are carrying out research that combines phenotypic measurements, ecological data, experiments, and genomics with the hope of shedding light on how local adaptation and speciation in Timema play out at the genomic scale.

Evolution of Aposematic Signals in the Poison Frog, Dendrobates tinctorius

The evolution of warning, or aposematic, signals has long intrigued biologists, however, the nature of natural selection acting on divergent aposematic phenotypes, under varying conditions (e.g. different densities of individuals possessing aposematic signals or different predator communities), remains relatively poorly understood.

Poison frogs belonging to the family Dendrobatidae possess bright colors that warn potential predators of toxins that the frogs accumulate in there skin from their diet. The great diversity of aposematic signals possessed by different species and populations of poison frogs makes them an excellent system in which to test the efficacy of different signal types under different ecological contexts.

Dr. Brice Noonan and I conducted two studies testing how predators perceive divergent aposemtic signals in different regions inhabited by the poison frog Dendrobates tinctorius. Specifically, we used clay models representing different aposematic signal types placed in regions where populations of D. tinctorius possess different local signal types as well as in two areas where D. tinctorius is found at different densities. Results of these studies can be found in: Noonan & Comeault (2009)Comeault and Noonan (2011).